When a ship with a Pointer attacks a settlement, a new Pointer is added to the settlement, regardless of whether it is captured or not, and without a Slaver involved anywhere! The ship still has its Pointer afterwards.

Did the settlements definitely not have the Pointers before the attack (from when they were created)?

When a ship crashes to become a settlement, it keeps the Buccaneers that were on the ship, until another ship is built there. I’m looking at the game and I can see that your other settlement - Rascals’ Refuge, also has a pointer.

The video explains all (consider the first fight and the dredging of the end): the enemy ship that should have sunk, hitten by my ship, it’s dredged by the same enemy. So now he has got the ship that was mine (right) and the ship that should have sunk (wrong).
In the end, another bug: the auto-dredged ship shows all the buccaneers that it has got before the sink.

Just to clarify a bit more on the dredging bug.
I sink Jean’s ship. Then I dredge Jean’s ship. Jean’s ship came back with two buccaneers on it, including one dredger. My other ship is sunk. It comes back under my control - presumably dredged by the ship I just took from Jean.

That’s interesting @Bessel - I just clarified in a different post that dredged ship is supposed to come back with 0 buccaneers. Any buccaneers that were on a ship when it was sunk are lost to Goblin Jones’ Locker.